Electrical fence charging apparatus



Oct. 14, 1941. N. F. AGNEW ET AL 2,258,669

ELECTRICAL FENCE CHARGING APPARATUS Filed June 6, 1939 ff I Whg? Patented Oct. 14, 1941 ELECTRICAL FENCE CHARGING APPARATUS Norman F. Agnew and Willard P. Place, Wilkinsburg, Pa.

Application June s, 1939, serial No. 277,676

(ci. 25e-1o) 12 Claims.

Our invention relates to electrical fence charging apparatus and more particularly to apparatus of this character which is safe, reliable and effi- Y cient in its operation.

One feature of our invention is the provision of an initial biasing charge on the fence or enclosing conductor which renders the voltage impulses more effective, thus making it possible to decrease the size and cost oi' the apparatus. Another feature of our invention is that a residual charge is left on the enclosure which provides a measure of protection during a temporary power outage or other interruption of the impulse voltage. A furtherfeature of our invention is the provision of apparatus which may be either manual or automatic or both, for indicating the integrity of the system. A still further advantage of our system is the provision of apparatus for preventing the fiow of an excessive short-circuit current in the chargedconductor, thus increasing the safety factor of the system. An added advantage is involved in what may be conveniently termed a trigger action of the apparatus in that a contact with the charged conductor, though occurring between impulses, causes the immediate discharge of an impulse, thus providing the desired warning shock immediately upon contact with the conductor and making it possible to use fewer impulses per unit of Atime with a. resulting saving in power input. vOther objects, features and advantages of the apparatus will become apparent from the description which follows. l

We shall describe two forms of electrical fence charging apparatus embodying our invention and shall then point out the novel vfeatures thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of electricall fence charging apparatus embodying our invention. Fig. 2 is a diagrammatic view showing a modified form o1' the apparatus of Fig. 1, also embodying our invention. Figs. 3 and 4 are voltage curves showing certain characteristicsof the apparatus of Figs. 1 and 2.

Similar reference characters refer to similar parts in each of the several views.

In apparatus employing a charged circuit for preventing farm stock or other animals from leaving an enclosure, it is desirable to establish a potential suiliciently high to provide the necessary warning shock, yet of such character as to create no damage or undue distress to the animal coming in contact therewith. A further reason for making the charged conductor effective for its purpose yet comparatively harmless is, of course, the likelihood of accidental contact therewith by children or others. With these and other important considerations in mind, our apparatus is so designed that it delivers a voltage of relatively high instantaneous value, but of comparatively short duration and having very low maximum current intensity. Moreover, the apparatus is so designed and arranged that a failure of any part thereof will not render the apparatus unsafe or hazardous.

Referring first to Fig. 1 of the drawing, the step-up transformer TI has a primary winding 4 connected to a suitable source of alternating current (not shown) which may, for example, be the usual volt, 60 cycle commercial source. The secondary winding has a mid-tap which divides the winding into two substantially equal portions 5 and 6 connected respectively to the anode terminals PI and P2 of a suitable full-wave rectifying tube RT. A third winding 'l of transformer TI supplies the heating current for the heater element F of the tube.

The output of the tube RT is impressed across a circuit which may be traced from the cathode C, wire 8, switch arm SI, resistors RI and R2, condenser CI, primary winding 9 of impulse transformer T2, and wires I0, II and I2,'back to the transformer TI and the respective anode terminal PI or P2. 'Ihe purpose of condenser C4 is to enable a higher output voltage to be provided since the condenser is maintained at the crest ,voltage value delivered by the tube RT. This condenser is not essential, however, and may be dispensed with, if desired. The resistor RI is of relatively high value as compared with resistor R2, and its purpose aswell as the purpose of the switch SI will be brought out more fully hereinafter.

Across a portion of the circuit just traced, namely, across resistor R2, condenser CI and impulse winding 9, is connected a. discharge tube DTI which may be of any suitable type, such as a neon or glow discharge tube either with or without a starter anode. 'I'he tube DTI is designed to have a. critical breakdown potential such that after a predetermined charge is supplied over the charging resistor RI and is accumulated by the condenser CI, the tube will break down and will cause a rapid rush of current in winding 9, thus inducing a voltage of high peak value and relatively short duration in winding I 3 of the impulse transformer T2. The ohmic value of the discharge resistor R2 is quite low as compared with RI in order that a substantial amount of energy impulse transformer. If sufcient resistance is present -in winding 9 of the impulse transformer, the discharge resistor may be dispensed with.

As soon as a suflicient charge is dissipated from condenser CI and the tube voltage reaches its critical cut-oil.' value, tube DTI will cease conducting, thus causing another change in the flux condition of transformer T2 whereby a small reverse-impulse will be delivered from winding I3. The constants of resistors RI and R2, condenser CI, and transformer T2 are so chosen with respect tothe characteristics of the tube DTI as to provide a cyclic charge and discharge operation of condenser CI and a periodic discharge of tube DTI at a rate whiciemay, for example, be of the order of 40 times per minute.

'I'he impulse voltage from winding I3 is applied (through condenser C3 and switch arm S3) between the ground wire I4 and the stock enclosing conductor or guard wire I5 which is insulated from ground. The guard wire I5 may be an insulated fence wire or any other suitable stock enclosing conductor or group of conductors exposed to electrical contact by livestock or other` enclosed animals, but insulated from the ground.

Itis apparent therefore that between wire I5 and ground there will recurrently appear sharp impulses of potential whereby an unpleasant shock will .be administered to stock coming in contact with the wire. Condenser C3 is of relatively low impedance to the impulse energy and serves to intensify the voltage output by providing a residual or biasing potential which maintains an initial charge on wire I5 at all times and which adds to the potential delivered by the impulse.I

transformer T2. This condenser is charged over a circuit which may be traced from the cathode C of tube RT, through the resistor R5, wire I5, condenser C3 and wires I0, II, and I2, to the center tap of transformer TI and one or the other anode of tube RT. In this manner, the peak voltage delivered by the apparatus is substantially increased without requiring a corresponding increase in the voltage capacity of the impulse generating elements of the system. Moreover, by virtue of the presence of the charged condenser C3, the guard conductor I5 will be maintained partially effective even though operation of the impulse generating apparatus may be temporarily interrupted for any reason, such for example, as a failure of the tube DTI.

Referring for the moment to Fig. 4 which shows the general appearance of the voltage impulses which are impressed on Wire I5, it will be noted that condenser C3 may be used to provide the bias voltage a in the diagram, the impulse transformer being then required to supply only the portion b of the resultant voltage c which is eective on the charged conductor. The bias a may, for example, be of the order of 400 volts,

Whereas c may be of the order of two to three times this value; thus b need only be of the order of 400 to 800 volts. The duration of an individual impulse may be of the order of 0.003 second. These values are of course only illustrative and may be widely departed from, in practice.

v l 2,258,669 may be quickly discharged by the tube into the not been shown in this diagram for simplicity. For a very long fence, or if the conductor I5 has considerable electrostatic capacity to ground, the duration of an impulse will be somewhat longer and it may have a somewhat lower peak value, unless the apparatus is so proportioned as to take care of the increased load represented by the capacity to ground.

Referring again to Fig. 1, the resistor R5 is of relatively high resistance and in normal operation with the guard wire ungrounded, no appreciable potential drop will appear across this resistor. When a ground develops, however, a substantial potential drop will appear across resistor R5 due to the ground leak and this drop may be used to provide an indication of whether or not an excessive ground exists on the charged conductor. The resistor R5 provides a path for the flow of current into condenser C3 and if the lnsulation of the system is high, the current owing through the resistor will be comparatively small but will increase substantially should an accidental ground develop, thus establishing the required indication potential. A discharge tube DT2 designed to break down at or below the potential drop effective during the grounded condition but to remain normally non-conducting,

' may be used across resistor R5 to provide a suitable visual indication of the grounded or ungrounded condition of the charged conductor.

Referring now to the manually operable switch arms SI, S2 and S3, these arms are mechanically connected in such a manner that when arm SI is moved from its normal or intermediate position 2 to either of its extreme positions I or 3, the arms S2 and S3 will be caused to assume corresponding positions. Position l is what We shall term the testing position and is provided for the purpose of determining whether the system is in its proper operating condition and no excessive leakage or short-circuit exists between the charged conductor and ground. Switch arm SI is biased by means of a spring so that it will automatically return to its normal position 2.

When the switch arms occupy the testing position I, the condenser CI instead of being charged through the usual charging resistor RI,

will now be charged through the ground resistance between wires I l and l5. The charging path for condenser CI will now extend from cathode C, wire 8, switch SI in position I, wires I1 and I6, ground resistance between wires I5 and I4, switch arm S3 in position I, resistor R4, wires 20 and I9, resistor R2, condenser CI, winding 9, and wires I0, I I and I2, to the transformer TI and anode PI or P2 of tube RT. Resistor R4 is merely a protective resistor which serves to guard the tube DTI in the event of a low resistance ground on conductor I5.

If the conductor I5 is well insulated, the effective resistance through which the condenser CI is charged will have a very high value which will be of about the same order of magnitude as that of the usual charging resistor RI. Accordingly, with the switch arms in position I under this condition, the rate atwhich the tube DTI will charge and discharge will be about the same as that obtained in normal operation, with the switches in position 2. lf, however, a ground is present on wire I5, the rate of charge and discharge will undergo a marked increase, whereupon the tube DTI will ash rapidly and so will provide a simple and direct visual indication of the grounded condition. By means of the testing provision which we have embodied in our ap- 2,258,669 paratus, it is possible to' check the effectiveness of the system periodically in a simple andconvement manner without in any way disturbing the apparatus or its permanent connections.

The purpose of the switch position 3 is to make possible an increase in the strength of the discharge from conductor I8 under certain conditions. We have found from experience that during the training period of the cattle or other` livestock, when the charged conductor is first used, it is desirable to administer a somewhat stronger impulse than that which'will later sufnce, once the animals have learned to approach the 'conductor with a certain amount of caution.

Accordingly we shall term position 3 the "train-- ing" position. When the switch arms occupy the training position 3, the capacity of condenser C2 is added to that of condenser CI by virtue of switch S2 so that a greater amount of energy is stored and is accordingly discharged through the impulse transformer. The charging resistor' R3 which now replaces resistor RI due to movement of the switch SI is of lower resistance in order that the increased charge may readily flow into the condensers CI and C2 in parallel. The greater charge will, of course, increase the energy which is discharged through the impulse transformer, making it possible to intensify the discharge from this transformer so as to render the conductor I5 more effective for its purpose. From oscillographicmstudies, we have found that the actual increase in open circuit voltage with the switches in the training position 3 is not very great, but there is a marked increase in the short-circuit current, and a smaller decrease in the voltage which remains effective when a given load is connected between the conductor I5 and ground.

Referring again to the biasing condenser C3, we have found that this condenser performs an additional function in that it tends to compensate automatically for changes in the moisture condition of the ground. 'I'he amount of surface moisture determines largely the resistance of the contact between an animal and ground and so influences the voltage which is necessary on the charged conductor. When the ground is dry and increased voltage is needed, the insulation of conductor I5 will also be greater because its supporting insulators will then be dry, so that condenser C3 will receive its full charge and will maintainl this charge. AWhen, however, the ground is wet and less voltage is required,

apparatus of Fig. l.4 The chief difference resides in the elimination of resistors R2 and RI, equivalent resistances being introduced into the windthe insulation resistance of conductor I 5 will also .y

be lower, so that condenser C3 will receive less charge and the effective voltage output will be lower. One advantageous result of this arrangement is that the dry weather condition does not make it necessary to increase the energy output of the impulse apparatus. Were it not for the presence of condenser C3, increased energy would Vhave to be stored in condensers CI and C2 with a resultant increase in the short-circuit current which is obviously undesirable both from an energy as well as a safety standpoint. We have found, for example, that a short-circuit current of the order of 100 milliamperes is ample and the apparatus may be designed with inherent current-limiting features for this purpose. One convenient way of accomplishing this result is to introduce resistance into the impulse transformer windings or introduce high leakage reactance into this transformer, or both.

Referring now to Fig. 2, we have shown in this figure a slightly modified arrangement of the vhas been accumulated in condenser CI.

of the apparatus, a certain ings themselves ofthe impulse transformer T2. A resistor R3 has also been introduced in series with the discharge tube DT2 in order to protect this tube as well as to limit the short-circuit current in the event of tube breakdown and a ground on the charged conductor occurring simultaneously. f

Except for a slight rearrangement of the circuit of transformer T2 to make the connections more simple and direct, the circuits and operation of the apparatus of Fig. 2 are essentially the same as that of Fig. l and need not be repeated in detail. It will be sumcient to say that condenser CI is charged over the resistor RI and discharges through the tube DTI and winding I, as before. Similarly, the impulse potential generated in winding I3 is added to the potential of condenser C3 so that the resultant peak voltage appears between the charged conductor I5 and -ground. The condenser C3 is maintained .con-

stantly charged over a similar circuit to that described in connection with Fig. l. Also, the testing position I and training position 3 of the switch arms perform the same functions as previously described. If desired, the filament of the rectifier tube RT may be connected with the cathode by means of the connection 2| to fix the filament potential and this, of course, can also be done in Fig. 1.

An important advantage which is present in the apparatus of both Figs. 1 and 2 is that a contact with the charged conductor, though occurring at a time between succeeding impulses, hastens the discharge of the apparatus and acts as a trigger to release the accumulated charge immediately upon contact. This can perhaps be best understood from the voltage diagram of Fig. 3 in which we have attempted to show the results of oscillographic observations pertaining to this particular feature of operation. The underlying reasons for this phenomenon are somewhat complicated and we do not deem it necessary for an understanding of .our invention to present these reasons in detail. It will be sufficient to say that a contact with the charged conductor induces a corresponding charge in winding 9 of the impulse transformer T2 which accelerates the discharge of the tube DTI.

Assuming, for example, that the conductor I5 is touched at some time such as indicated at d in Fig. 3, in between the usual periodic impulses,

' we have found that after a small reverse pulse,

there follows immediately the main impulse Without the necessity for waiting during the usual interval between impulses. This first impulse may or may not have as high a peak as the usual impulses, depending upon how much charge Succeeding impulses such as g and h will then follow in the usual order and will be timed from the impulse f. Were it not for the trigger" action time would elapse between contact with the conductor and the occurrence of the succeeding impulse i, shown dotted in the diagram. This time might be sufficient to enable an animal to escape through the enclosure. To put the matter in another way, this feature of our apparatus makes it possible to space the impulses much farther apart, with a resulting decrease in power input and without any sacrifice in the protective features of the apparatus.

'In order to provide a general idea oi' the re1- ative magnitude of certain constants of the apparatus of Fig. 1, for example, we have found that with an output of about 325 volts delivered from each of the windings 5 and 6 of transformer TI, one set of values of the various condensers and resistors of the apparatus giving satisfaclltory results may be as follows: condensers ('Jlv and C2, 2=microfarads each; condensers C3 and Cl, 0.25 microfarad each; resistors RI, R3 and R5, 0.5 megohm, 0.2 megohm, and 0.1 megohm, respectively; resistor R2, 6 00 ohms; and'resistor R4, 10,000 ohms. For' the rectifying'tube RT anddischarge tube DTI, the tubes designated commercially as 6ZY5C;V and OA4G, respectively, were found to be suitable. An impulse transformer T2 having a step-up ratio of the order of 7 to l was found to be satisfactory.

With apparatus such as above, and switch arms occupying the normal position 2, the peak charge on conductor I5 is of the order of 1000 volts and the bias provided by condenser C3 is of theorder of 400 volts. The parts are so proportioned that the maximum current obtainable from the apparatus is Well within a safe value so that the apparatus is incapable of administering an injurious shock. This safety feature has been-borne out 'by numerous tests of the apparatus under actual service conditions. The foregoing values may obviously be varied widely to suit the conditions of a particular installation by proper lselection of the circuit constants, discharge tubes, transformer ratios, etc., as will be readily apparent to those skilled in the electrical field.

It will be understood that we have set forth certain numerical values solely for the purpose of providing a more clearv understanding of the general proportions of the apparatus and not in any limiting sense whatsoever. It will be clear that any or all of these values may be widely changed, as desired, tomeet the requirements of a given installation such, for example, as the prevailing value of insulation resistance of conductor I5 to ground, moisture content of the soil in the vicinity of the charged conductor, type of livestock to be herded, etc.

From the foregoing description, it will be apparent that we have provided apparatus which is simple, compact, safe and highly effective in its operation. 'By eliminating all moving parts, the reliability of the apparatus has been greatly increased whereas the cost as well as the necessity for frequent adjustment and maintenance have been substantially decreased.

Although we have herein shown and described only two forms of apparatus embodying our inlvention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

1. In combination, a source of unidirectional current, a shock administering condenser, a resistor, means for charging said condenser from said source through said resistor, an impulse transformer, a discharge device, means for discharging said condenser through the input winding of said transformer and said discharge device when the accumulated charge on said condenser reaches the breakdown potential of said discharge device, said discharge occurring periodically at a rate determined by the constants of said resistor, said condenser and said discharge device to thereby induce periodic voltage impulses of suiliciently high peak valueffor shock purposes in the output winding ,of sarid impulse transformer, a bias condenser conne ted in the output circuit oi' said transformer, eans for charging vsaid bias condenser from said unidirectional source, anenclosing conductor, and means for impressing said voltage impulses augmented by the charge from said bias condenser between saidenclosing conductor and ground.

2. Apparatus forproviding a stock enclosure by means of a charged conductor comprising, in

combination with said conductor, means Yfor producing periodic voltage impulses of sufciently high peak value for shock purposes, a condenser for providing an initial bias on said conductor, means for maintaining said condenser in a charged condition, and means for impressing said voltage impulses augmented by said initial bias from said condenser between said conductor and ground.

3. Apparatus for providing a stock enclosur by means of a charged conductor comprising, in combination with said conductor, means for producing periodic voltage impulses of relatively high peak value but of relatively low available power, means for maintaining an initial charge upon said conductor, and means for impressing said voltage impulses between said conductor and ground, whereby both said initial charge and said impulses cooperate to increase the effectiveness of said conductor by increasing the peak voltage on the conductor.

4. Apparatus for providing a stock enclosure by means of a charged conductor comprising, in combination, an impulse transformer having its output winding connected with said conductor; means including the input winding of said transformer, a discharge device, and an energy storing device for periodically causing a discharge from said energy storing device through said discharge device and input winding to thereby impress recurrent voltage impulses of relatively high peak value from said' output winding on said conductor; an auxiliary energy storing device for providing a bias on said conductor, and means for causing energy to be stored in said auxiliary device, said auxiliary device being connected with said output winding in such manner that contact between said conductor and ground will release energy stored in said auxiliary device through said impulse transformer to thereby accelerate the discharge from said discharge device.

5. In an electrically charged enclosure-in combination, a discharge device coupled inductively with said enclosure for impressing periodic voltage impulses of relatively high peak value on said enclosure, and means including a constantly energized energy storing device for providing a bias on said enclosure, said device being connected with said enclosure in such manner that contact between said enclosure and ground will release energy stored in said constantly energized device, thereby reacting on said discharge device through the inductive coupling so as to cause an acceleration of said impulses.

6. In combination with an electrically charged Y enclosure, means for providing an initial charge on said enclosure, means for periodically im- Maaate 7. In combination with an electrically charged enclosure, means for providing an initial charge on said enclosure, means including a discharge device for periodically impressing voltage impulses oi' predetermined power upon said enclosure to cooperate with said initial charge and so to increase the charge on said enclosure, and means i'or attimes increasing the energy discharged by said discharge device to thereby increase the power of said impulses so as to increase the eiectivenessof said enclosure.

8. Apparatus for providing a stock enclosure by means of a charged conductor comprising, in

tor, a source of current, means for establishing a shocking potential from said source between said conductor and ground, a condenser connected between said conductor and ground, and means for charging said condenser from said source and adding the charge thereof to said shocking l potential to thereby increase the magnitude of combination, a condenser, a discharge device, a

charging resistor, a source'of unidirectional current, a circuit closer having a iirst position in which said condenser is intermittently charged from said source over said resistor to thereby cause a periodic discharge from said device to` be impressed upon said conductor, means for at times causing said circuit Vcloser to assume a second position in which said charging resistor is excluded and said condenser is charged from said source through the resistance between said conductor and ground, and means for biasing said circuit closer to said rst position.

9. In combination with an enclosing conductor, means for establishing a shocking potential between said conductor and ground, and means including a condenser connected `between said conductor and ground for augmenting. said shocking potential and for automatically compensating the potential effective on said conductor in accordance with the insulation resistance o! said conductor to ground whereby the efiiciency ot said conductor is maintained both in wet weather and in dry weather.

10. In combination with an enclosing conducsaid V'potential and to automatically compensate said potential in accordance with the insulation resistance of said conductor to ground, whereby the eiilciency of said conductor is maintained both in wet-weather and in dry weather.

ll. In electric fence charging apparatus including a fence conductor which is charged for providing a stock enclosure, the combination of means for producing periodic voltage impulses oi sumciently high peak value for shock purposes, a condenser for providing an initial bias on the fence, means for maintaining said condenser in a charged condition, and meanslfor impressing said voltage impulses augmented by said initial bias from said condenser between the fence and ground.

12. In electric fence charging apparatus including a fence conductor which is charged for providing a stock enclosure, the combination of means for producing periodic voltage impulses of relatively high peak value but of relatively low available power, means for maintaining an initial vcharge upon the fence, and means for impressing said voltage impulses between. the

' fence and ground, whereby both said initial charge and said impulses cooperate to increase the effectiveness of the fence by increasing the peak voltage thereon.

NORMAN F. AGNEW. WILLARD P. PLACE. 

